Aging-related muscle wasting and weakness (sarcopenia) is an important problem of an increasingly aging society (Faulkner et al. 2007; Manini et al. 2007). Though sarcopenia is a multifactorial phenomenon, a number of studies have indicated the presence of marked denervated and atrophied muscle fibers (Chai et al. 2011; Valdez et al. 2010; Tomlinson et al. 1977; Oda et al. 1984; Kawamura et al. 1977). Indeed, using electromyographic techniques that allow longitudinal monitoring of motor unit function in the mouse in vivo (Arnold et al. 2014), a reduction in the number of functional motor neurons innervating the hind limb muscles have been identified as an early feature in aging mice. The motor unit is comprised of a single motor neuron and the muscle fibers it innervates. Motor unit synaptic connectivity is maintained by trophic support from various compartments (Fu et al. 2008; Koliatsos et al. 1993; Ikeda et al. 1995; Kablar et al. 2005), and it is suggested that the maintenance of motor neuron connectivity and repair of neuromuscular junctions (NMJs) is critical in aging.
Peripheral nerves are commonly injured from trauma including automobile accidents, motorcycle accidents, surgeries, knife and projectile wounds and birth injuries to both the child and mother. Common surgical causes of nerve injury include prostatectomy and mastectomy. Other common injuries during surgery are the result of long-term limb positioning or inevitable or accidental nerve compression. Following nerve injury there is a loss of sensation and/or function in the regions of the body innervated by the damaged nerve. For example, following nerve injury from prostatectomy there is commonly erectile dysfunction. Following mastectomy there is often loss of proper function of the upper extremity and/or scapula. Furthermore, following birth injury or other trauma with damage to the brachial plexus there is dysfunction in the ipsilateral limb. What is needed are methods and compositions related to treating sarcopenia and nerve injury in a subject in need thereof.